A Metal–Ligand Cooperative Pathway for Intermolecular Oxa‐Michael Additions to Unsaturated Nitriles

Abstract

An unprecedented catalytic pathway for oxa-Michael addition reactions of alcohols to unsaturated nitriles has been revealed using aPNN pincer ruthenium catalyst with adearomatized pyridine backbone.The isolation of acatalytically competent Ru-dieneamido complex from the reaction between the Ru catalyst and pentenenitrile in combination with DFT calculations supports amechanism in which activation of the nitrile through metal-ligand cooperativity is akey step.The nitrile-derived Ru-N moiety is sufficiently Brønsted basic to activate the alcohol and initiate conjugate addition of the alkoxide to the a,b-unsaturated fragment. This reaction proceeds in aconcerted manner and involves asix-membered transition state.These features allow the reaction to proceed at ambient temperature in the absence of external base. Scheme 1. Catalytic addition of isopropanol to 2-pentenenitrile (2-PN) and 3-pentenenitrile (3-PN).

Phosphine‐NHC Manganese Hydrogenation Catalyst Exhibiting a Non‐Classical Metal‐Ligand Cooperative H2 Activation Mode

“…[13] Theresulting complex (4), showing methylation of the carbon atom linking the phosphine and NHC moieties, was isolated as am ixture of two diastereomers (ratio 6:1) differing by the position of the methyl group with respect to the iodine atom (Scheme 2, middle). [14,15] These results clearly indicated that the deprotonation of 2 occurs at the CH 2 bridge forming as ufficiently nucleophilic carbon species to react with electrophiles such as MeI or CO 2 . In asecond experiment, the deprotonated species was exposed to CO 2 (1 atm) affording the complex 5 in 89 % yield (Scheme 2, bottom), whose solid state structure highlights the existence of atripodal NHC-phosphine-carboxylate scaffold with af acial arrangement of the carbonyl ligands ( Figure 1d).…”

Phosphine‐NHC Manganese Hydrogenation Catalyst Exhibiting a Non‐Classical Metal‐Ligand Cooperative H2 Activation Mode

“…In asecond experiment, the deprotonated species was exposed to CO 2 (1 atm) affording the complex 5 in 89 % yield (Scheme 2, bottom), whose solid state structure highlights the existence of atripodal NHC-phosphine-carboxylate scaffold with af acial arrangement of the carbonyl ligands ( Figure 1d). [14,15] These results clearly indicated that the deprotonation of 2 occurs at the CH 2 bridge forming as ufficiently nucleophilic carbon species to react with electrophiles such as MeI or CO 2 .…”

Cooperative Binding of SO2 under M–O and C–S Bond Formation in a Rhenium(I) Complex with Activated Amino- or Iminopyridine Ligand

“…The activation of CO 2 involving C-nucleophilic actor ligands has attracted increased attention and was recently reviewed by Song and co-workers . In this regard, the role of MLC-triggered activation/binding of CO 2 was discussed for various complexes. − Recent studies also concern the MLC-triggered activation of multiple bonds such as carbonyls and CN-multiple bonds − in complexes with pyridine-based pincer ligands. Against this background, we herein report the extension of the substrate scope to S=O bonds, as complex 1 readily reacts with the adduct of 1,4-diazabicyclo[2.2.2]­octane and sulfur dioxide (DABSO), which is a convenient source of SO 2 , to give the sulfinate compound fac- K­[Re­( amidopy-OSO )­(CO) 3 ] ( 2ab ) under Re–O and C–S bond formation (Scheme , 2ab ).…”